The heart is a hollow muscular organ with four pumping chambers: the left and right atria and the left and right ventricles. One-way valves between each of the chambers control the flow of blood in and out of the heart. The valves that control the blood flow between the atria and the ventricle are termed as Atrio-Ventricular Valves while the valves between the Ventricles and the outflow tracts are Outflow Tract/Semi-lunar Valves. The left atrio-ventricular valve is called the Mitral Valve, while the left ventricular outflow tract valve is called the Aortic Valve. Similarly, the right atrio-ventricular valve is called the Tricuspid Valve, while the right ventricular outflow tract valve is called the Pulmonary Valve.
Heart failure related to heart valve dysfunction is a widespread condition in which one or more of the heart valves fail to function properly. The dysfunction of the valves is mainly divided into two types: a) Valve Stenosis—wherein the effective flow orifice area of the valve is decreased due to various reasons and there is significant obstruction to the forward flow through the valve and b) Valve Incompetence—wherein the valves do not close properly and there is excessive retrograde leakage of blood when the valve is closed. Both types of these disease lead to debilitating effect on the performance of the heart and could also lead to congestive heart failure.
Surgery to repair damaged valves is the method of choice over valve replacement in the current surgical era. Surgical repair techniques involve reconstruction or controlled alteration of the geometry of the native valve using implantable devices. One of the most common repair technique used today by the surgeons to repair atrio-ventricular valve regurgitation is annuloplasty, in which the valve annulus is geometrically stabilized or reduced in size by suturing a prosthetic annuloplasty ring onto the annulus. The annuloplasty rings are designed to roughly conform to the shape of the annulus and maintain ample leaflet coaptation and allow good forward flow. There are also specific annuloplasty rings that have a non-physiological shape and upon implantation conform to the shape of the atrioventricular valve annulus to their non-physiological shape. These annuloplasty rings are generally made in different shapes, sizes and mechanical properties. D-shaped annuloplasty ring is the most common among the shapes with two important sub-categories being the full ring and a partial ring. The rings are also made rigid, semi-flexible and flexible that claim to allow the restoration of the native valve kinematics.
Implantation of these rings requires surgical intervention with an open-chest and the patient on cardiopulmonary bypass for a significant period. Surgical skill is of utmost importance in creating the sterna incision or thoracotomy and in opening the left atrial wall to provide exposure of the mitral valve. Using current techniques, once the annuloplasty ring is implanted it can neither be changed in shape nor size, and thus choice of the optimal annuloplasty ring type with required geometric characteristics is key for post-operative success. Minimally invasive procedures that can implant annuloplasty rings at the location of interest through less invasive techniques may decrease post-operative risk and reduce the patient mortality.
The present invention has particular relevance to the repair of dysfunctional tricuspid valves using both invasive and minimally invasive techniques. The tricuspid valve 10 regulates the flow of blood between the right atrium and the right ventricle. The tricuspid valve 12 has three main components—the tricuspid annulus 12, the three leaflets 14, 16, 18 and the three papillary muscles (not shown). The annulus 12 of the valve is a fibro-muscular ring from which the three leaflets 14, 16, 18 (anterior, septal and posterior) originate and regulate the flow through the valve orifice. The leaflets 14, 16, 18 extend inward into the valve or flow orifice defined by the annulus 12. There are three commissures between the three leaflets, which include an anteroseptal commissure 22, a posteroseptal commissure 24 and an anteroposterior commissure 26. Fibrous chordae tendineae extend from the three leaflets 14, 16, 18 and insert into the three papillary muscles extending from the heart muscle. The papillary muscles located in the right ventricle hold the leaflets and restrict them from prolapsing into the right atrium. The tricuspid annulus 12 is an ovoid-shaped fibrous ring, which is not very prominent and is larger in the circumferential area and different in shape than the mitral valve.
Generally, both mitral and tricuspid regurgitation occur simultaneously in a patient. Moreover, in the past tricuspid insufficiency was considered as a silent and almost benign disease which was a subsequent complication of mitral insufficiency, and therefore, if mitral insufficiency was corrected, tricuspid insufficiency would revert by itself. Recent Studies by Matsaguna et. al. 2005 have shown the contrary, even after mitral regurgitation is corrected surgically, tricuspid regurgitation persists and grows with time. The presence of tricuspid insufficiency results in increased mortality and accelerated progression of heart failure in a significant patient population. Therefore, there is a significant need to create devices and procedures which may correct tricuspid regurgitation.
Currently most atrioventricular valve repair technologies are tailored to repair the mitral valve, since this valve is generally more susceptible to disease. Therefore, it is commonplace to use annuloplasty rings designed for the mitral valve in the tricuspid position. Since the geometries of the native mitral (bicuspid valve) and tricuspid (three cusps) valves is significantly different, repairs of the tricuspid valve with mitral technologies has produced substandard long term results for patients with tricuspid disease. Therefore, there is a need for the development of annuloplasty devices tailored to the tricuspid valve geometry. Additionally, the annulus of the tricuspid valve is proximal to the AV Node of the heart in the triangle of Koch, a fundamental component of the electrical circuit of the heart. Suturing through this node, which can and happened during tricuspid repair causes heart block, complication which then needs to be addressed with a pacemaker. As a result there is a need for tricuspid annuloplasty devices that are optimally designed to the native tricuspid valve annular shape and which protect the AV node during implantation and prevents heart block. Finally, annuloplasty ring sizing on the tricuspid position is more complex than in the mitral position due to the lack of well-defined reference points in the tricuspid annulus. Therefore it would be of significant benefit to have a tricuspid annuloplasty device which can be adjusted in shape or size in order to improve patient outcome.
Despite multiple annuloplasty methods and devices currently on the market, there is a continued desire to improve such methods and devices. Particularly, there is a desire to have devices and methods that better accommodate the anatomy of the heart valve and the shape of the heart valve components throughout the cardiac cycle, and thereby improve results associated with valve repair surgery.